Synopsis After carrying out a series of practice circuits and landings, the pilot returned to the airport for a full-stop landing. Shortly after touchdown, the aircraft veered off the runway and ran into a creek. The aircraft was substantially damaged and the pilot was seriously injured. The Board determined that the pilot lost control of the aircraft on landing; the reason for the loss of control could not be determined. The severity of the pilot's injuries and the damage to the aircraft were attributed to the aircraft's collision with the bank of the creek. Contributing to the accident was the hazard presented by the uncovered watercourse's orientation to the runway, its presence within the boundary of the strip, and its proximity to the threshold of runway 24. 1.0 Factual Information 1.1 History of the Flight The pilot had been practising landings at the Chilliwack Municipal Airport, British Columbia. After completing a few circuits, he positioned the aircraft for a full flap, full- stop landing on runway 24. Just after touchdown, the left wing rose and the aircraft began to veer left. It continued to turn with only the nosewheel and right main wheel in contact with the ground until it ran off the left side of the runway about 900 feet from the threshold (see Appendix A). Once on the grass, the aircraft began to skid sideways and the left main wheel made contact with the ground. The aircraft was now yawed about 10 degrees to the left of its direction of travel, and its forward speed was about 40 knots. The aircraft ran through the short grass, out of the pilot's control, for about 150 feet until it ran into a 10-foot deep creek oriented at a 90-degree angle to the runway. The aircraft's nosewheel entered the creek about 48 feet from the left edge of the paved runway. The aircraft became momentarily airborne until its nose crashed heavily into the far bank of the creek. The aircraft then settled into the shallow water in the bottom of the creek. 1.2 Pilot Egress The pilot was unrestrained by a shoulder harness, and was flung forward into the instrument panel when the aircraft struck the side of the creek. The force of the impact pushed the aircraft's nose back into the cabin and trapped the pilot in his seat. Rescue personnel used the jaws of life to extract him from the aircraft. He was seriously injured; the aircraft was substantially damaged. 1.3 Weather The airport temperature was about 20 degrees Celsius, the sky was clear, and the visibility was unrestricted. The surface wind was less than 10 knots and from about 210 degrees magnetic. The crosswind component for runway 24 was about six knots. 1.4 The Pilot The pilot was certified and qualified on the aircraft type. 1.5 The Aircraft The maintenance log-books contained no evidence of uncorrected deficiencies relevant to the circumstances of the occurrence. An examination of the aircraft after the occurrence revealed no evidence of a malfunction that would cause the aircraft to veer to the left on landing. The aircraft was serviced and maintained in accordance with existing directives. The weight and centre of gravity were within the prescribed limits. The aircraft was not equipped with a shoulder harness, nor was one required by regulation. 1.6 The Landing The pilot did not remember much about the landing. A witness said that the aircraft first touched down on its nosewheel and then bounced back into the air. Other witnesses saw the aircraft's wings rocking from side-to-side as it landed. Skid marks on the runway revealed that only the nose and right main wheels were on the runway as the aircraft began to veer to the left, and that the left main wheel did not touch the ground until the aircraft had run off the edge of the runway. The aircraft then began to skid sideways. Except for the creek, there were no other obstacles in the path of the aircraft. 1.7 Porpoising and Wheelbarrowing Porpoising is oscillation about the aircraft's lateral axis in the manner of a porpoise. A landing porpoise is an oscillation (bouncing) set up between the aircraft's nose and main wheels, and can occur when the nosewheel contacts the runway first, either as a result of excessive landing speed or faulty pilot technique. Wheelbarrowing is a condition that arises when the nosewheel rather than the main gear is forced to support an abnormal share of the aircraft's weight. Touching down on the nosewheel, excessive braking, or friction between the wheels and runway caused by a side-skid may cause wheelbarrowing. Wheelbarrowing can damage a nosewheel or cause an aircraft to yaw uncontrollably off its intended course. 1.8 TP 312 - Aerodrome Standards And Recommended Practices The Chilliwack runway was certificated by Transport Canada (TC) as Category 2(B) non- instrument. As such, the airport's manoeuvring areas must comply with certain established parameters, as defined in TC publication TP 312 - Aerodrome Standards and Recommended Practices The TP 312 in effect at the time of the occurrence (1991) was dated 06 February 1986. The current edition is dated 01 March 1993. Excerpts from both editions are found in Appendix B. 1.9 Strips - Definition The current TP 312, at article 3.1.6.5, states that, A strip including a non-instrument runway shall extend on each side of the centre line of the runway and its extended centre line through the length of the strip, to a distance of at least 30 meters (98.5 feet) where the code number is 1 or 2. 1.10 Category 2(B) Standards - Graded Areas - Definition The current TP 312 requires a Category 2(B)1 runway to be 75 feet wide and to have a 75-foot graded area on each side of the centre line extending along the full length of the runway and stopway where provided. The Chilliwack runway conforms to Category 2(B) standards. 1.11 Drainage Ditches The TP 312 standard for drainage ditches in effect in 1991, the time of the occurrence, directed that drainage ditches located at the edge of the graded area adjacent to the runway be contoured in order to reduce structural damage should an aircraft inadvertently overrun the ditch. Open ditches should have a side slope of 4 units of horizontal measure to 1 unit of vertical measure. The maximum side slope acceptable shall be 3 units of horizontal measure to 1 unit of vertical measure. Open ditches shall be graded and sodded for erosion control and ease of maintenance. Drainage ditches were not to be located within the graded portion of the strip. 1 Category 2 refers to an aeroplane reference field length of 2,650 feet up to but not including 4,000 feet. The current TP 312, amended March 1993, also states at article 3.1.6.19 that, Drainage ditches shall not be located within the graded portion of the strip. Where drainage ditches are located at the edge of the graded area, they shall be contoured in order to reduce structural damage in the event an aeroplane overruns the ditch. TP 312 further recommends at article 3.1.6.21 that: Open ditches should have a side slope of 4 units of horizontal measure to 1 unit of vertical measure. Open ditches should be graded and sodded for erosion control and ease of maintenance. 1.12 The Chilliwack Airport The north/south creek was located in the undershoot area of runway 24 before that runway was extended. The course of the creek was altered when the runway was extended, and a culvert now runs under the 75-foot-wide and 3,900-foot-long runway about 1,250 feet from the threshold of runway 24. The culvert then empties into open ditches. The north ditch begins 79.5 feet from the runway centre line and the south ditch begins 77.5 feet from the runway centre line. Thus, the ditch begins beyond the graded portion of the strip. The creek is about 52 feet wide on average and 10 to 15 feet deep, with a side slope steeper than 1:3. Its edges and steep rocky sides are covered with vegetation. At the time of the accident, three to four feet of water covered its bottom; the depth of water, however, varies with precipitation. Both the north and south outlets of the under-runway culvert are located within the confines of the aerodrome strip and at the edge of the graded area. 1.13 TC Interpretation of TP 312 TC does not consider the creek which the aircraft struck to be a drainage ditch, but rather a watercourse, or naturally occurring stream. TC cites runways built beside rivers and lakes as examples of similar naturally occurring hazards. TC contends that the TP 312 standard for drainage ditches normally refers to those that are parallel to runways; however, TP 312 does not specifically address orientation. 1.14 Previous Accident An accident involving the same uncovered creek occurred during a runway excursion in 1988 (A88P0188). The pilot lost directional control of the aircraft during a rejected take-off, and the aircraft ran into the creek.